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Full text of "Flora Indica Vol-I"

INTRODUCTORY   ESSAY                                    97
A vegetation of a different nature from any of the above
prevails in the extratropical regions of India during the cold
months only ; and, 'though contrasting in character with that
of tropical animals,, is dependent upon analogous modifications
of climate/for its ^presence. This consists of annual plants
of the north temperate zone that do not appear within the
tropics (except at a considerable elevation), and which owe
their southward extension into India to the winter's cold, just
as the summer annuals owe their northward extension to the
heat. These flo'wer when the tropical plants arc torpid : they
are very numerous, comprising many European and cosmo-
politan genera, and even species. .Besides the winter crops of
the Gangetic plain, consisting of Wheat, Barley, and more
rarely Oats, with various kinds of pulse, there are, of wild
plants, Ranunculus sceleratus and muricatus, Capsdla Bursa-
pastoriSy Silepe conica, Alsine media, Arenaria seiytyllifolia,
Euphorbia HeUoscopta, Mgdicago lupulina and denticulata, La-
thyrus Aphaca, Gnaphalta, XantJdum, Veronica agrestis and
Anagallis, Helwtropium Europaum, various Polygona, Juncus
bufonius, Buiomus umbellatus, Allsma Plantayo, and very many
Cyperacea, Grasses, and such aquatics as MyrwpUyllum, Po-
tamoyeton natans and crispus, Vallisneria, Zannichellia, Ra-
nunculus aquatifas, Lemna, and many others.
The transition from the tropical to the temperate Flora
is more rapid in ascending above the level of the plains,
than in advancing northward at the same level; the change
of vegetation in a few thousand feet of ascent being much
greater than in as many degrees of latitude as would com-
pensate for the decrease of temperature experienced in that
nsccnt. In the perennially humid provinces of India the
climate of the base of the mountains is even moilc equable
than that of the adjacent plains, from the atmosphere being
more loaded with moisture. Hence in these regions' a warm
temperate Flora (neither strictly temperate nor markedly tro-
pical) conmiciiees at elevations of 2-3000 feet, and prevails
over the purely tropical, which appears in scattered trees,